Such vacuum chambers can be used in a switchgear assembly whose gas, such as air, is an insulating gas that can be at atmospheric pressure. Consequently, an insulating cylinder, covers and a bellow can be configured in terms of strength for atmospheric pressure. Cases are conceivable in which the vacuum chamber is installed in a switchgear assembly whose pressure is substantially increased, for example, up to approximately 25 bars, with the result that the parts as mentioned before should all be configured such that they withstand this pressure.
Known circuit breakers provide protection for electrical systems from electrical fault conditions such as current overloads, short circuits, and low level voltage conditions. Circuit breakers can include a spring-powered operating mechanism which opens electrical contacts inside a vacuum interrupter to interrupt the current flowing through the conductors in an electrical system in response to abnormal conditions. Vacuum interrupters can include separable main contacts disposed within an insulated and hermetically sealed vacuum chamber.
The vacuum chamber can include one or more sections of ceramics for electrical insulation and one or more metal components to form an envelope in which a vacuum may be drawn. The metal components can be easily formed and can provide a structural strength lacking in the ceramic components. The ceramic shell can be cylindrical. However, other cross-sectional shapes can be used. The metal components can include two end caps and, where there are multiple ceramic sections, one or more external center shields disposed between the ceramic sections.
EP 1 742 242 B1 discloses a metal component for a vacuum chamber of a circuit breaker, wherein the vacuum chamber has at least one electrically insulating hollow body. The metal component includes a body structured to be coupled to the hollow body, and a sealing edge extending from the body. The sealing edge has a distal tip with a sealing surface, and a gradual reduction in cross-sectional thickness between the body and the sealing surface, so that the sealing surface is the thinnest portion of the sealing edge. The sealing edge is generally circular with the inner and outer surfaces thereof defined by respective inner and outer diameters. The gradual reduction in cross-sectional thickness is created by the inner and outer diameters becoming respectively smaller and larger as measured from a point adjacent to the sealing surface to a point adjacent to the body.
U.S. Pat. No. 7,508,636 B2 relates to a vacuum chamber with at least one insulating cylinder made of ceramic material. The face ends of the ceramic insulating cylinder are closed off by a cover, each with a movable contact element attached to a movable contact stem and with a fixed contact element attached to a fixed contact stem, which each penetrate the cover. Furthermore, a vacuum-tight sealing element is fastened between the one cover and the movable contact stem and permits a movement of the contact stem. The covers are tightly soldered or brazed to the respective face end of the adjacent insulating cylinder by interposing at least one supporting ring. The sealing element is fastened to the cover and the contact stem. The covers are provided with a cup-like arrangement and include an edge which is thinner relative to the remainder of the area. The sealing element includes two or more layers which are connected, and especially welded or brazed, with their free ends in a vacuum-tight manner with each other and with the cover and the contact stem, respectively.